Luke Shaw's style is making the word 'full-back' redundant to be replaced by 'liquid flank-curator' or 'premium side-run man'. Photograph: Henry Browne/Action Images

Football can at times look like a seductively simple business. In the rush to dissect the now-concluded David Moyes mini-era at Manchester United there is a temptation to conclude that Moyes never quite recovered from his first major piece of business at the club. From the outside the signing of Marouane Fellaini at the end of a fraught and almost fruitless summer transfer window always looked like an act of mild desperation, the footballing equivalent of a man who has been sat trying to decode the menu at some impossibly swish French brasserie, cheeks flushing as he reads the words "foie gras ivre de Château Chalon mitonné doucement en cocotte" for the 17th time, and who finally hurls his menu to the floor and says: "You know what, I'll just have the full English."

With this in mind it feels like a good moment to offer instead a round of departing applause for what looks like being Moyes' last major piece of business at the club, and in many ways a brilliantly contrasting bookend to the Fellaini deal. By all accounts the transfer of Luke Shaw from Southampton will go through in the summer, with Moyes having worked right to the end with an air of burning-deck nobility to tie down the deal.

It could yet turn out to be an excellent and also rather poignant bit of business, and not just because Shaw already looks a brilliantly cloudless talent, an insistent, physically imposing presence who like all the best hyper-mobile, modern full-backs always wants the ball, always wants to be involved, convinced at all times that left-back is no longer simply where the game ends up – a kind of plughole from where it must be discreetly tweezered out and re-set, but is instead the place where the real action starts and ends, a last ungentrified repository of space in an otherwise congested field.

There is even a departing paradox here, as Shaw is exactly the kind of signing that would have looked so reassuringly big-time and austere and tacitly astute if it could only have been Moyes' first act at United rather than his last. Full-backs: they're so hot right now! It is above all an aspirational position these days, a statement of what kind of team you really want to be, and a role no longer peopled by frazzled-looking bandy-legged men constantly on the verge of some form of sprawling athletic humiliation, but instead by long-striding athletes with an air of hair-gelled historic ascendancy about them, glamour boys of the withdrawn defensive flank.

Full-backs have for years been quietly dominant figures in the Premier League, where the congestion of central areas has transformed the full-back into a possession magnet and conductor of the play. Against Real Madrid in midweek the great positional fetishist Pep Guardiola asked his Bayern Munich full-backs to be three things at once, defender, ball-carrier and auxiliary midfield cog, the kind of thoroughgoing rejig that suggests even the word full-back, which dates back to the 1870s and the first real notion of defence in football, might be heading for the chop soon, to be replaced by something more appropriate like liquid flank-curator, or inverted wing-ferret or premium side-run man.

It is all quite surprising given the history of the modern full-back, a position that was conceived out of necessity, a reaction to more urgent developments elsewhere, specifically the change in the offside law in 1926 that saw Herbert Chapman's Arsenal lead off with the W-M formation, with wingers pushed wide and long lateral passes the vogue. Out of this the old school marking, full-back was born, cast from the start as a straight man, an Ernie Wise kind of footballer, a patsy for the jinking winger.

Alf Ramsey experimented with overlapping full-backs at Ipswich Town and later with England. And the full-back continued to thrive through the fluid Dutch-West German dominance of the 1970s, a time of frowning, sideburned inspirational men in brilliant block-coloured kits, and of a growlingly intellectualised ideal of frictionless total football in which attacking full-backs were a high-fashion item. Plus, of course, South America has always had its own way with attacking full-backs, from Djalma Santos to the magnificent Javier Zanetti, who could have played anywhere, who could have been an astronaut or a heroic handsome cowboy, but who chose instead to be a great and indestructible marauding right-sider.

It is a process that has come late to English football. Ashely Cole has been an expertly sure-footed defensive full-back, England's best tournament footballer during those painful recent rearguard dramas of departure. And in the last few years there has been a broader shift. Seamus Coleman and Leighton Baines (signed by Moyes for less than £7m the pair) have been perhaps the most high-profile parts of the carefully-maintained Model T Ford Moyes left carefully tucked away inside the Goodison Park garage with a note and a spare set of keys, and in which Roberto Martínez has so obviously enjoyed haring around corners with the top down and generally revving about the place with eye-catching abandon.

Meanwhile news of an exciting young full-back coming through tends to draw the same curiosity – there is already talk about Southampton's Calum Chambers, who will apparently be Luke Shaw after Luke Shaw has been Luke Shaw – as an exciting young centre-forward once did.

We should, of course, be careful. Shaw may or may not go on to fulfil his potential but is for now an uplifting, state of the art, young English talent with a lovely, aristocratic kind of simplicity in his game, who looks also like the perfect modern signing for a heavyweight club in the process of reinventing itself. For Moyes and United he could end up being a wonderful, and wonderfully pointed parting gift.